Passenger Car Response to Interaction with Tractor-Trailer Steer Tire Lugs

Performing a reconstruction of sideswipe interactions is difficult due to the lack of permanent crush sustained by the vehicles involved. Previous studies have provided insight into the forces involved in creating various types of damage for vehicle-to-vehicle interactions during a sideswipe interaction. However, these data may not be applicable to the interaction that occurs when a tractor-trailer steer tire is involved. As demonstrated in previous studies, steer tire interaction produces a unique pattern of markings on the struck vehicle by the protruding lugs (wheel stud) of the steer tire. These studies have demonstrated that the pattern of cycloidal marks created by the wheel lugs can be used to calculate the relative speeds of the vehicles. While this is helpful in understanding the relative motion of the vehicles, it does not provide information regarding the forces applied at the point of contact. The purpose of this study is to assess the structural response of passenger cars during a sideswipe event involving a tractor-trailer steer tire. The study consists of quasi-static and dynamic tests performed using a stationary tractor-trailer tire spinning at an equivalent speed of 55 mph. A total of 20 quasi-static tests were performed using 3 separate vehicles by forcing the spinning tire against the side of a stationary vehicle. The force and displacement necessary to cause various levels of damage to the passenger car was measured to develop an understanding of the stiffness response at different locations along the side of the vehicle. A range of contact stiffness was achieved by forcing the tire against areas around the door pillars and at the center of the door panels which produced stiffer and softer responses respectively. A total of 8 dynamic tests were performed by driving the side of the same 3 vehicles against the rotating steer tire. The vehicle acceleration and change in speed (Delta-V) associated with contact were measured. Peak forces during the quasi-static testing ranged from 500 to 2,600 lbs with a range of deflection of 0.5 to 3.6 inches. The data provided by the quasi-static testing can be used to assess the lateral forces applied to passenger vehicles based on the level of damage sustained. The dynamic testing was performed at speeds of 4.5 to 6.5 mph and resulted in peak vehicle accelerations of 0.1 to 1.4 g in the lateral and 0.1 to 0.6 in the forward direction. The patterns created by the wheel studs were similar to those presented in previous studies. The results of the dynamic testing can be used to assess vehicle acceleration based on the severity of the damage observed.